1. Field of the Invention
The present invention relates to internal combustion engines and more particularly to methods and systems for controlling temperature of exhaust gas aftertreatment devices used with such engines.
2. Background of the Invention
As is known in the art, exhaust gas aftertreatment devices are generally used with vehicular internal combustion engines. One type of such device is a particulate filter type device. Such (PF) device traps carbon particles from the exhaust gas stream of the engine. Over time, PF becomes occluded with carbon particles. If allowed to continue, flow through PF can become impeded. To avoid deleterious effects on the engine, the PF is regenerated by the reaction of soot with NO2 or O2. In the former PF regeneration method, an oxidation catalyst is placed upstream of the PF or the PF is coated with precious metal, thereby oxidizing NO in the exhaust gas to NO2 for regeneration of the PF. To efficiently generate NO2, the oxidation catalyst or the PF are above 300 degree C. Effective PF regeneration by the latter PF regeneration method occurs when the temperature of PF is above 450 degrees C. Such temperature is exceeded when the engine is at a high load operating condition. However, it is not always possible for the engine to operate at such a high load condition to provide the removal of the particulates.
As a consequence, the prior art contains a variety of methods to cause the PF to attain regeneration temperature including: electrical heating, operating auxiliary devices to cause the engine to operate at a higher load condition than otherwise required to provide desired torque, injecting additional fuel in the exhaust, and others. These methods increase the engine's fuel consumption.